Traditionally, actually for centuries, needle access to the epidural space around the spine has been achieved with a technique known as “loss of resistance”. During this technique, the operator will normally use a small gauge (18G to 14G, and more typically, 18G or 17G) needle and a syringe of saline or air attached to the hub of the needle. The needle is advanced through the skin and underlying tissue until it engages the ligament layers over the spine and epidural space. As the needle is advanced through the soft tissue underlying the skin, the operator exerts constant pressure on the plunger of the syringe, which is attached to the hub of the needle. When the needle is within ligament, there is considerable resistance on the plunger. However, when the needle passes into the epidural space, the resistance is gone or lost and the plunger advances easily at this point thereby informing the operator through tactile response that the tip of the needle has been introduced into the epidural space.
Physicians are trained to use typically 17 and 18 gauge needles in most instances. Accordingly, the tactile response with needles of this gauge is very familiar to the operator. For best clinical practice, this precise tactile feedback should be maintained to optimize the chances of properly identifying the epidural space.
It is also common practice to introduce large bore sleeve needles generally referred to as introducer needles into the epidural space for introduction of larger elements, such as paddle, flat or wire leads, into the epidural space. For example, see U.S. Pat. Nos. 7,022,109; 6,553,264; 6,309,401; 6,249,707; 6,245,044; 5,669,882 and 5,255,691.
The gauge of such introducer sleeve needles exceeds that which is familiar to the operator, and accordingly, use of the loss of resistance technique is impossible when introducing the tip of such an introducer sleeve needle into the epidural space.
The gauge of such introducer sleeve needles is not always specified, and for example, in U.S. Pat. No. 6,309,401 it is based on size of the paddle leads to be inserted through the introducer needle, and therefore would need to be 10 gauge or larger.
In the prior art, the method normally used to introduce such an introducer sleeve needle into epidural space is to attach a syringe to the large oblong introducer hub, and attempt to use the loss of resistance technique. However, in this case, the precision of the tactile feedback from such a large bore needle is lost and this provides a significant negative impact on the success rate of the procedure for introducing an introducer sleeve needle into the epidural space.
Other problems are also incurred. With respect to the introducer sleeve needle disclosed in U.S. Pat. No. 6,309,401, a hub is fixed to the body of the introducer needle and cannot be removed. In order to pass paddle leads through the introducer sleeve needle, the leads would have to pass through the hub at some point. The hub would either be too small to pass the paddle leads, or it would have to be as large an opening as the diameter of the oblong introducer to fit the paddle leads therethrough. In the first instance, the operator would not be able to pass the leads through the device. In the latter case, the operator would never find a syringe with the proper fitting to mate with the hub to even attempt a loss of resistance technique. Furthermore, in the latter instance, there would be a complete loss of tactile feedback to the operator as the introducer sleeve needle is advanced making it extremely risky and difficult to identify the epidural space.
It is a principal object of the present invention to eliminate these aforementioned risks and shortcomings, and to provide an epidural needle assembly for safely introducing a large bore introducer sleeve needle into the epidural space of the spinal column of a patient and for inserting wide lead elements, or multiples thereof, into the epidural space. The invention also uniquely provides for the simultaneous introduction of multiples of lead elements into the epidural space or other subcutaneous tissue layer.